document.write( "Question 115300: A small lake is stocked with a certain species of fish. The fish population is modeled by the function
\n" ); document.write( "P=10/1+4e^-0.8t \r
\n" ); document.write( "\n" ); document.write( "where, P is the number of fish in thousands and t is measured in years since the lake was stocked. \r
\n" ); document.write( "\n" ); document.write( "The fish population (correct up to two decimal places) after 3 years is______
\n" ); document.write( "(Remark: don't forget to use the correct units for P .) \r
\n" ); document.write( "\n" ); document.write( "The fish population reaches 5000 after years is __________ (correct up to two decimal places).
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Algebra.Com's Answer #84091 by ankor@dixie-net.com(22740)\"\" \"About 
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A small lake is stocked with a certain species of fish. The fish population is modeled by the function
\n" ); document.write( "P = \"10%2F%281%2B4e%5E%28-0.8t%29%29\"
\n" ); document.write( "where, P is the number of fish in thousands and t is measured in years since the lake was stocked.
\n" ); document.write( ":
\n" ); document.write( "The fish population (correct up to two decimal places) after 3 years is______
\n" ); document.write( "(Remark: don't forget to use the correct units for P .)
\n" ); document.write( ":
\n" ); document.write( "Substitute 3 for t in the given equation:
\n" ); document.write( ":
\n" ); document.write( "P = \"10%2F%281%2B4e%5E%28-0.8%2A3%29%29\"
\n" ); document.write( "P = \"10%2F%281%2B4e%5E-2.4%29\"
\n" ); document.write( "Find e^-2.4 on a good calc:
\n" ); document.write( "P = \"10%2F%281%2B4%2A.0907%29\"
\n" ); document.write( "P = \"10%2F1.623\"
\n" ); document.write( "P = 7.34 thousand
\n" ); document.write( ":
\n" ); document.write( "The fish population reaches 5000 after years is __________ (correct up to two decimal places).
\n" ); document.write( ":
\n" ); document.write( "P = 5
\n" ); document.write( "5 = \"10%2F%281%2B4e%5E%28-0.8t%29%29\"
\n" ); document.write( ";
\n" ); document.write( "Multiply both sides by = \"%281%2B4e%5E%28-0.8t%29%29\"
\n" ); document.write( "5\"%281%2B4e%5E%28-0.8t%29%29\" = 10
\n" ); document.write( ":
\n" ); document.write( "Divide both sides by 5:
\n" ); document.write( "\"1%2B4e%5E%28-0.8t%29\" = 2
\n" ); document.write( ":
\n" ); document.write( "Subtract 1 from both sides and you have:
\n" ); document.write( "\"4e%5E%28-0.8t%29\" = 1
\n" ); document.write( "Divide both sides by 4
\n" ); document.write( "\"e%5E%28-0.8t%29\" = .25\r
\n" ); document.write( "\n" ); document.write( "-.8t = ln(.25); remember the ln(e) = 1
\n" ); document.write( ":
\n" ); document.write( "-.8t = -1.3863
\n" ); document.write( "t = \"%28-1.3863%29%2F%28-.8%29\"
\n" ); document.write( "t = 1.733 years
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check solution by using 1.73 for t in the original equation and find P
\n" ); document.write( "P = \"10%2F%281%2B4e%5E%28-0.8%2A1.73%29%29\"
\n" ); document.write( "P = \"10%2F%281%2B4e%5E-1.3863%29\"
\n" ); document.write( "P = \"10%2F%281%2B4%2A.25%29\"
\n" ); document.write( "P = \"10%2F%281%2B1%29\"
\n" ); document.write( "P = 5 which is 5000 fish
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